The invention relates to a fastening arrangement for fastening a component to a another member using a thread-forming screw.
In harsh environments, stainless steel panels are often used as structural components, housings, and the like, to minimize corrosion problems. It is frequently necessary to mount various components to such panels, or to fasten two or more such panels together, using threaded fasteners such as screws. Desirably, thread-forming or self-tapping screws would be used in such circumstances so that tapped pilot holes would not have to be formed in the panels. However, thread-forming screws are generally made of mild steel or the like, and stainless steel is substantially harder than mild steel. Generally, a thread must be created using a harder material to cut or form the thread; commonly available fasteners are not harder than stainless steel.
With most thread-forming fasteners, the thread formation starts on the circular edge of the pilot hole that lies in a plane normal to the axis of the screw (i.e., the edge defined by the intersection between the cylindrical inner surface of the hole and the planar outer surface of the panel). The thread of the fastener is at a shallow angle to this circular edge. For a thread-forming fastener to work, the thread must remain largely intact after breaking into this edge. Generally, on stainless steel the soft thread is damaged on this edge and is unable to pass through it.
The shallow angle between the fastener thread and the edge of the hole, and the limited ability of the screw to form the harder material, make it very difficult to form threads in stainless steel.
As a result of the difficulties of using thread-forming fasteners in stainless steel, it is typically necessary to use an alternative approach to fasten items to stainless steel panels. For instance, threaded inserts, rivet-nuts, weld nuts, and clip-in nuts are common solutions. Unfortunately, each of these solutions adds additional parts and operations, ultimately increasing product cost.